Add advice meow--prepare-face to enable-theme instead of load-theme (#488)

* Add advice `meow--prepare-face` to `enable-theme` instead of `load-theme`

Add advice `meow--prepare-face` to function `enable-theme` instead of
`load-theme`. This will help prepare faces if a theme is enabled with
`enable-theme`. The modification does not change the current behavior,
because `enable-theme` is called at the end of `load-theme`, and calling
`load-theme` also triggers advice on `enable-theme`.

* Use a wrapper of `meow--prepare-face` as an advice to `enable-theme`

Adding advice `meow--prepare-face` to `enable-theme` instead of `load-theme`
(commit 64bdbee) causes `meow--prepare-face` being called twice when a theme
is enabled. This commit uses a wrapper of `meow--prepare-face` as the
advice. The wrapper calls `meow--prepare-face` only when the theme to
enable is `user`.

Author: HardGraphite

meow-core.el

@@ -160,6 +160,11 @@ there's no chance for meow to call an init function."
   (when (secondary-selection-exist-p)
     (meow--cancel-second-selection)))
 
+(defun meow--enable-theme-advice (theme)
+  "Prepare face if the theme to enable is `user'."
+  (when (eq theme 'user)
+    (meow--prepare-face)))
+
 (defun meow--global-enable ()
   "Enable meow globally."
   (setq-default meow-normal-mode t)
@@ -190,7 +195,7 @@ there's no chance for meow to call an init function."
     (setq redisplay-highlight-region-function #'meow--redisplay-highlight-region-function)
     (setq redisplay-unhighlight-region-function #'meow--redisplay-unhighlight-region-function))
   (meow--prepare-face)
-  (advice-add 'load-theme :after 'meow--prepare-face))
+  (advice-add 'enable-theme :after 'meow--enable-theme-advice))
 
 (defun meow--global-disable ()
   "Disable Meow globally."
@@ -210,7 +215,7 @@ there's no chance for meow to call an init function."
     (setq redisplay-unhighlight-region-function meow--backup-redisplay-unhighlight-region-function))
   (unless window-system
     (meow-esc-mode -1))
-  (advice-remove 'load-theme 'meow--prepare-face))
+  (advice-remove 'enable-theme 'meow--enable-theme-advice))
 
 (provide 'meow-core)
 ;;; meow-core.el ends here